A travelator, moving ramp or escalator, collectively referred to herein as a people mover, comprises a conveyor. Such a conveyor is known to include a frame, which comprises a first frame part secured to a fixed structure and a second frame part mounted to be movable with respect to the first frame part in its longitudinal direction, the first and second frame parts being mounted one after the other. A first drive element is located on a first side of the conveyor and implemented as an endless loop. A second drive element is disposed on a second side of the conveyor at a distance from and parallel to the first drive element and implemented as an endless loop. A plurality of conveyor platforms, such as pallets or stairs, are arranged one after the other and secured to the first drive element and the second drive element. A first wheel is disposed on the first side at a first end of the conveyor and mounted with bearings on the first frame part, the first drive element being passed over the first wheel. A second wheel is disposed on the first side of the conveyor at a second end and mounted with bearings on the second frame part, the first drive element being passed over the second wheel. A third wheel is disposed on the second side at the first end and mounted with bearings on the first frame part, the second drive element being passed over the third wheel. A fourth wheel is disposed on the second side at the second end and mounted with bearings on the second frame part, the second drive element being passed over the fourth wheel. A first tensioning device is disposed on the first side and arranged to act between the first frame part and the second frame part to force the first wheel and the second wheel flexibly away from each other to tension the first drive element with a first tensioning movement. A second tensioning device, disposed on the second side of the conveyor, is of a construction substantially identical with the first tensioning device and arranged to act between the first frame part and the second frame part to force the third wheel and the fourth wheel flexibly away from each other to tension the second drive element with a second tensioning movement. By tensioning the drive element, a drive element tension suitable in respect of operation of the conveyor is maintained.
Today, however, there is a need for travelators, moving ramps and/or escalators in which the transport distances are very long and in which the distance between the wheels of the drive elements are consequently also very long. For example, in very long travelators, the distance between the wheels can be long, e.g. on the order of 100 meters.
Further, there has arisen a need for low-construction travelators, moving ramps and escalators designed to be mounted directly on a fixed base, such as a floor, without any special pits formed in the fixed structure, such as the floor of a building, for embedded mounting of the frame and machinery of the travelator. In the low-construction frame structure of a travelator, moving ramp or escalator mounted on a fixed base there is very little space for the drive machine of the conveyor, and therefore the diameter of the wheels has to be quite small and consequently the chain must have a small pitch (e.g. 15 . . . 20 mm). Thus, the number of chain links subject to wear over the length of the chain must be fairly large and the chain undergoes much larger elongation than conventionally. This means that the tensioning device must have a fairly long stroke (e.g. 300 . . . 400 mm). Also, the difference of elongation (due to uneven load or the like) in each chain is quite large. As the transport platforms are fastened to the chains, different elongation of the chains means that the transport platforms are not in a straight position when moving, and this leads to problems in the operation of the conveyor.
Usually the chains used in travelators and escalators are long-pitch drive chains (typically having a pitch of 100 . . . 200 mm). As the number of links subject to wear over the length of the conveyor is relatively small, the elongation is relatively small. Therefore, the chain tensioning device need not have a long stroke (typically <100 mm) and the elongation of each chain is relatively small. Thus, there has been no need for compensating the elongation.